1. Field of the Invention
The present invention relates to a photoelectric conversion device and a manufacturing method thereof.
2. Description of the Related Art
Recently, a photoelectric conversion device that generates power without carbon dioxide emissions has attracted attention as a countermeasure against global warming. A typical example of the photoelectric conversion device is a solar cell for supplying residential power or the like, which generates power from sunlight outdoors and in which single crystal silicon, polycrystalline silicon, or the like is used. Further, a thin-film solar cell including amorphous silicon that can be produced at low cost is known.
Although an amorphous-silicon solar cell can be used for supplying residential power or the like, there is a problem in that when the amorphous-silicon solar cell is irradiated with strong light, light deterioration occurs and the initial conversion efficiency decreases. The amorphous-silicon solar cell has a high photoelectric conversion capability with respect to wavelength of visible light such as light of a fluorescent lamp. Accordingly, the amorphous-silicon solar cell is used for operating a device with low power consumption such as a calculator or a wristwatch in many cases.
A thin film photoelectric conversion device is easily processed to have high integration to obtain a desired voltage. An integrated photoelectric conversion device includes an isolation groove that separates stacked semiconductor layers into a plurality of cells. The isolation groove is also used as a connection groove that connects a cell to an adjacent cell in series. The connection groove is provided with a conductive material. Thus, for example in the case where a cell has a pin-type structure, since a side surface portion of each semiconductor layer is in contact with the conductive material provided in the connection groove, the semiconductor layer is short circuited to a rear electrode and an upper electrode. Since each semiconductor layer has high resistance, a current flows in the lateral direction of a cell is very low, a state in which the side surface portion is short-circuited does not become a practical problem. Note that a “cell” in this specification refers to a minimum unit of a photoelectric conversion region that constitutes an integrated photoelectric conversion device.
However, in the case where a cell has a multi-junction type structure such as a tandem type structure, a low resistance layer such as a layer doped at high concentration or a light-transmitting conductive film is used in a region where cells are connected in the vertical direction. Accordingly, when integration is performed in the above-described manner, a leakage current is high and thus favorable electric characteristics cannot be obtained.
To solve this problem, Patent Document 1 discloses a method in which a plurality of first regions (cells) which are to be photoelectric regions and a second region that is positioned between the first regions are formed, and a connection groove is formed in the second region so that short circuit between a semiconductor layer or a light-transmitting conductive film in the first region and a conductive material provided in the connection groove is prevented.
[Reference]
    [Patent Document 1] Japanese Published Patent Application No. 2004-260013